Folks:
I have been scrutinizing the RDF Schema Specification 1.0, and am greatly puzzled by something that doubtless I'm not the first to stumble over.
In traditional O-O programming languages, the relationship "subclass" occurs only between two classes, while "type" occurs between class and instance (ie: "variable", not a another class).
In the RDF Spec, mention is made that the RDF Type System has some differences from O-O, and it appears from the diagrams that one of the differences is that a thing can be both an *instance* of some class (via the type relation) and at the same time a *subclass* of some other class.
Could this mean that any instance contains enough metastructure info that it can also function as a class? Or only some instances can do this? Or???
Regardless, we seem to end up with the odd position of having two kinds of relationship that superficially are engaged in transmitting characteristics to "decendants"... and the RDF Spec is very ambiguous as to what the difference is between the two mechanisms.
Given that this is a feature of RDF most novel or indeed counter-experience to O-O practitioners, may I suggest that a clearer discussion be mustered to nail down exactly what are the intended distinct applications of these two kinds of relationship?
Regards,
Graham
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Graham Wideman
Resources for programmable diagramming at:
http://www.diagramantics.comgraham@wideman-one.comhttp://www.wideman-one.com